Electronic Circuits and Tutorials
Electronics Schematics - M

Modulators Circuits

12 Volt or 24 Volt DC Pulse Width Modulator: This circuit can be used as a light dimmer or DC motor speed controller.

2 Transistor FM Transmitters:

3 Watt FM Transmitter:

68HC11 Function Generator:

Active clamp/reset PWM IC becomes more versatile: 06/26/03  EDN-Design Ideas / The UCC3580 (www.ti.com), IC1 in Figure 1, is an active-clamp/reset-PWM IC that has all the requisites of a power-supply IC except for current limit. You can use the shutdown pin (16) for this purpose (see the UCC3580 data sheet). But when the shutdown pin activates, the soft-start capacitor normally connected to Pin 15 discharges, and the converter starts again, resulting in hiccup mode.

Add on AM Modulator has High Bandwidth: 09/11/98 EDN-Design Ideas

AM / FM / SW Active Antenna: This circuit shows an active antenna that can be used for AM, FM, and shortwave SW. On the shortwave band this active antenna is comparable to a20 to30 foot wire antenna. This circuit uses receivers that use untuned wire antennas, such as inexpensive units and car radios. L1 can be selected for the application

AM Receiver:

AM Transmitter:

Basic FM Radio Transmitters:

Circuit makes simple FSK modulator: 10/11/2001 EDN - Design Ideas / The need for a compact telemetry system poses a challenge for designing a small, light, low-component-count system. Interfacing serial data from the microprocessor is also difficult because most low-cost RF transmitters do not accept dc levels at the input. Commercial FSK (frequency-shift-keying) modulators are bulky and need many passive components.

Circuit sequences supplies for FPGAs: 01/23/03  EDN-Design Ideas / System designers must consider the timing and voltage differences between core and I/O power supplies (in other words, power-supply sequencing) during power-up and power-down. The possibility of a latch-up failure or excessive current draw exists when power-supply sequencing does not occur properly.

Class B Series Modulator:

Current Amp Provides Frequency Modulation: 12/04/97 EDN-Design Ideas

DC to Pulse Width Modulator: This control circuit is suitable for the accurate control of DC motors, lighting levels, small heaters as well as other applications. The circuit converts a DC voltage into a series of pulses, such that the pulse duration is directly proportional to the value of the DC voltage. This circuit can operate with 8-35VDC and control up to 6.5A current. The control voltage is adjustable (can be tuned for0-10-Volt DC).

Digital Potentiometer Controls Phase Shift: 02/15/96 EDN-Design Ideas

Digitally Controlled Phase Shift: Altering the phase response of a signal without changing its amplitude characteristics is commonly performed using an all pass filter. This circuit implementation is well suited to using digital potentiometers as the controlling element.

Dual Voltage Controlled Filter with Modulator:

Dual Voltage Controlled Oscillator with Modulator:

Eight Channel Eight Bit PWM Controller: National Semiconductor Application Notes,05-Aug-1995

FM Beacon Transmitter (88 108 MHz): This circuit will transmit a continuous audio tone on the FM broadcast band (88-108 MHz) which could used for remote control or security purposes. Circuit draws about30 mA from a 6-9 volt battery and can be received to about100 yards.

FM Radio Bug:

FM Radio Telephone Bug:

FM Radio Telephone Transmitter:

FM Radio Transmitter #1:

FM Radio Transmitter:

FM transmitter :

FPGMakes Simple FIFO: 10/26/00 EDN-Design Ideas / PDF contains multiple circuits - scroll to find this circuit

Improved FM Stereo Modulator:

Improved frequency modulator uses "negatron": 07/11/2002  EDN - Design Ideas / You can improve a capacitive-sensor circuit with a modulator and an RF transmitter (Reference 1) by modifying the modulator portion to obtain better accuracy. More improvements result from adding a "negatron" circuit, a configuration that uses equivalent negative capacitance. Reference 2 gives some insight into the uses of negative impedance.

KD2BD AT Volt AM Video Modulator: video signal processing circuit that allows adjustment of video gain, video bias, sync and sync level

Limiting Amplifier Forms AM Modulator: 12/07/95 EDN-Design Ideas

Linear, MicroPower Pulse Width Modulator:

Low Cost Audio Video Modulator & Transmitter: project report in PDF format

Low Power FM Transmitter:

Micro Power AM Broadcast Transmitters: In this circuit, a 74HC14 hex Schmitt trigger inverter is used as a square wave oscillator to drive a small signal transistor in a Class C amplifier configuration. The oscillator frequency can be either fixed by a crystal or made adjustable VFO with a capacitor/resistor combination.

Micro Spy With FETs:

Micro Spy With TTL:

Micro Spy With USW:

MicroPower FM Broadcasting Circuits:

MicroPower Pulse Width Modulator:

Miniature FM Transmitter #1:

Miniature FM Transmitter #2:

Miniature FM Transmitter #3:

Miniature FM Transmitters #4:

Modulator Draws just 5 MAt 2.7V: 06/05/97 EDN-Design Ideas

Modulator's Design Cuts FPGA's Gate Count: 01/06/94 EDN-Design Ideas / The pulse-width modulator (PWM) macro in Fig1 requires only half as much logic as a conventional2-counter design. With the help of extra logic, a synchronous, loadable up/down counter can encode information in the duty cycle of a constant-frequency, constant-amplitude signal.  

MPF102 FM Receiver:

Non Powered Ring Modulator Circuit:

Novel LowCost QPSK Modulator Needs No Adjustments : 09/16/02 Electronic Design - Ideas for Design / Eliminating software adjustments in circuits based on digital logic improves robustness and reduces cost for small-production-run series. This circuit is a cost-improved version of classical QPSK modulator designs.

PCB Drill Controller: The speed controller in this article overcomes this problem by raising the voltage to the drill as the load is increased. The unit uses a basic Pulse Width Modulation (PWM) regulator to reduce the power dissipation.

Phase Shift Radio Direction Finder:

Phase Shifter Yields Slope Polarity Detection: 03/14/96 EDN-Design Ideas

Phase Shifter:

PLD Adds PWM SoftStart Function To Switching Power Supplies: 07/08/02 Electronic Design - Ideas for Design / Switching converters sometimes use soft-start circuitry to reduce the large in-rush current that occurs when they first turn on. By employing a PLD, soft start can be added to power-supply controllers that don't natively support this function.

Provide 4  to 20 MPWM Control: 09/01/98 EDN-Design Ideas /  Are useful when you use4- to20-mA current-loop signals to control a PWM signal

Provide 4to 20mPWM Control: 09/01/98 EDN-Design Ideas /  Are useful when you use4- to20-mA current-loop signals to control a PWM signal

Pulse Width Modulation DC Motor Control: controls the motor speed by driving the motor with short pulses

Pulse Width Modulators: generating PWM waveform is extremely simple with the circuits shown in this page

Pulse Width to Voltage Converter:

PWM Circuit uses one OpAmp: 07/06/00 EDN-Design Ideas / circuit delivers a rectangular signal with duty cycle varying between0 and100% in response to an input signal varying from0 to5V dc

PWM Controller: 555 Timer based PWM motor control project for electric fan or other DC motor

PWM Motor / Light Controller Variations: diagrams are for12V operation and there are high side (common ground) and low side (common +12V) versions

PWM Speed Control: includes theory and some example circuits

PWM Watchdog Circuit Ensures upper Bounds: 11/07/96 EDN-Design Ideas

Simple AM Radio Receiver & Amplifier:

Simple Circuit Provides Efficient PWM: 02/18/99 EDN-Design Ideas / PDF contains multiple circuits - scroll to find this circuit

Simple PWM ADC is Surprisingly Accurate: 06/09/94 EDN-Design Ideas

Simple PWM Signal Generator Suits Backlight LCD Applications : 04/15/02 Electronic Design - Ideas for Design / In LCD backlight applications, a dc-to-ac inverter drives cold-cathode fluorescent lamps. The inverter's input comes from the display's power supply.

Small FM Transmitter:

Stereo Ducker:

T Volt Modulator: This circuit uses an MC1373 to form a TV video modulator

Three Watt FM Transmitter:

Transistor pair lowers PWM IC's start up current: 03/18/99 EDN-Design Ideas / PDF contains multiple circuits - scroll to find this circuit

Two Transistor FM Transmitters:

Variations on the PWM DC Motor Speed Control:

VHF / UHF T Volt Modulator:  Elektor January1985

Voltage Controlled Mixer with Modulator:

Waveform Generator Demodulates FM Signals: 10/10/96 EDN-Design Ideas / PDF contains multiple circuits - scroll to find this circuit

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